1. Field of the Invention
This invention generally relates to mechanically decoupled opto-mechanical connectors for flexible optical waveguides embedded and/or attached to a printed circuit board. More particularly, the invention relates to improvements of an optical interface between the waveguides in an optical printed circuit board and associated opto-electronics or passive optics thereon.
2. Description of Background
Printed circuit boards (PCBs) generally include multiple integrated circuits mounted upon their surfaces. PCBs typically contain multiple conductive and dielectric layers interposed upon each other, and interlayer conductive paths (referred to as vias), which may extend from an integrated circuit mounted on a surface of the PCB to one or more conductive layers embedded within the PCB.
The speed and complexity of integrated circuits are increasing rapidly. As the number of components per chip, the number of chips per board, the modulation speed and the degree of integration continue to increase, electrical interconnects are facing fundamental limitations in areas such as bandwidth, bandwidth density, bandwidth times length product, packaging, and power consumption.
The employment of optical interconnects will be one of the major alternatives for upgrading the interconnection speed whenever conventional electrical interconnection fails to provide the required bandwidth. However, the introduction of optics and the required optical connections into the PCB causes problems due to the substantially different requirements than those of commonly utilized electrical interconnects, mechanical connectors, thermal interfaces, and the like. One problem is the proper connection of the waveguides in the board with waveguides in other boards, with opto-electronic modules on board, and with test equipment such as fiber bundles. For example, connections between the opto-electronic subassembly and the PCB would require electrical lines with high speed capability to the PCB, an optical coupling to the waveguides, mechanical connectors between the opto-electronic subassembly and the PCB as well as a thermal interface to the heat sink. Connections between boards would require optical connections with precise alignment, electrical lines, and rugged mechanical connections. Connection between the board and the test equipment would require optical connection with precise alignment and compatibility to standard fiber bundles. The different connections as noted above and the specific properties required for the connections, i.e., electrical, thermal (different coefficients of thermal expansion between dissimilar materials), and the like as well as the large tolerances in current PCB manufacturing processes, lead to numerous potential problems. For efficient optical coupling, the alignment accuracy of multimode polymer waveguides has to be in the range of 5 to 10 micrometers, whereas current PCB tolerances are in the range of about 100 micrometers.
Accordingly, there remains a need for improvement of the optical interface between an opto-enhanced printed circuit board and associated electronics thereon.